This invention relates to a new and improved pharmaceutical composition and method for delivery of bioactive substances. The methods and composition of the invention can be used with several agents and can achieve site specific delivery of a biologically active substances. This can allow for lower doses and for improved efficacy with drugs particularly agents such as oligonucleotides which are plagued with problems in achieving therapeutic concentrations at targeted organs.
Drug delivery techniques are employed in the formulation of all drug therapy to augment drug availability, to reduce drug dose, and consequently to reduce drug-induced side effects. These techniques serve to control, regulate, and target the release of drugs in the body. The goals have been to provide less frequent drug administration, to maintain constant and continuous therapeutic levels of a drug in the systemic circulation or at a specific target organ site, to achieve a reduction in undesirable side effects, and to promote a reduction in the amount and dose concentration required to realize the desired therapeutic benefit.
To date, drug delivery systems have included drug carriers based upon proteins, polysaccharides, synthetic polymers, erythrocytes, DNA and liposomes. New generation biologicals such as monoclonal antibodies, gene therapy vectors, anti-cancer drugs such as Taxol, viral based drugs, and oligo and poly nucleotides have presented several problems with regard to delivery. In fact drug delivery may be the primary hurdle to achieving mainstream therapeutic use of these biologics whose initial potential seemed unlimited but whose therapeutic parameters have prevented realization of full benefit.
Synthetic oligodeoxyribonucleotides which are chemically modified to confer nuclease resistance represent a fundamentally different approach to drug therapy. The most common applications to date are antisense oligos with sequences complementary to a specific targeted mRNA sequence. An antisense oligonucleotide approach to therapy involves a remarkably simple and specific drug design concept in which the oligo causes a mechanistic intervention in the processes of translation or an earlier processing event. The advantage of this approach is the potential for gene-specific actions which should be reflected in a relatively low dose and minimal non-targeted side effects.
Phosphorothioate analogs of polynucleotides have chiral internucleoside linkages in which one of the non-bridging ligands is sulfur. The phosphorothioate analog is currently the most commonly employed analogue in biological studies including both in vitro and in vivo. The most apparent disadvantage of phosphorothioate oligonucleotides include the high cost of preparation of sufficient amounts of high quality material and non-specific binding to proteins. Hence, the primary advantage of antisense approach (low dose and minimal side effects) fall short of expectations.
Drug delivery efforts with regard to oligonucleotides and polynucleotides have focused on two key challenges; transfection of oligonucleotides into cells and alteration of distribution of oligonucleotides in vivo.
Transfection involves the enhancement of in vitro cellular uptake. Biological approaches to improve uptake have included viral vectors such as reconstituted viruses and pseudo virions, and chemicals such as liposomes. Methods to improve biodistribution have focused on such things as cationic lipids, which are postulated to increase cellular uptake of drugs due to the positively charged lipid attraction to the negatively charged surfaces of most cells.
Lipofection and DC-cholesterol liposomes have been reported to enhance gene transfer into vascular cells in vivo when administered by catheter. Cationic lipid DNA complexes have also been reported to result in effective gene transfer into mouse lungs after intratracheal administration.
Cationic liposomal delivery of oligonucleotides has also been accomplished however, altered distribution to the lung and liver was experienced. Asialoglycoprotein poly(L)-lysine complexes have met with limited success as well as complexation with Sendai virus coat protein containing liposomes. Toxicity and biodistribution, however, have remained significant issues.
From the foregoing it can be seen that a targeted drug delivery system for delivery of biologics, particularly poly and oligo nucleotides is needed for these drugs to achieve their fullest potential.
One object of this invention is to provide a novel composition of matter to deliver a pharmaceutical agent to a targeted site in vivo.
Another object of the invention is to provide a method for delivering a pharmaceutical agent, increasing drug bioavailability and decreasing toxicity.
Another object of the invention is to provide a method of forming a novel composition of matter for delivering a pharmaceutical agent to a targeted site in vivo by sonicating perfluorocarbon containing microbubbles in a nitrogen-free environment.
Other objects of the inventions will become apparent from the description of the invention which follows.
According to the invention a new biologically active agent delivery method and composition are disclosed. The compositions and methods can be used to deliver agents such as therapeutics or diagnostics which have been plagued with delivery problems, such as oligonucleotides, as well as traditional agents and can drastically reduce the effective dosages of each, increasing the therapeutic index and improving bioavailability. This in turn can reduce drug cytotoxicity and side effects.
The invention employs conjugation of the biologic agent with a filmogenic protein which is formed as a protein shell microbubble encapsulating an insoluble gas. The composition is prepared as an aqueous suspension of a plurality of the microbubbles for parenteral administration. Conjugation of the biologic with albumin or other such protein encapsulated microbubbles can allow for targeted delivery of the biologic to alternate including those which traditionally interact with the protein.
Improved gas-filled microbubbles with enhanced stability and thus better delivery capabilities are achieved by forming the microbubbles in the presence of a nitrogen-free environment. The nitrogen-free environment makes microbubbles which are significantly smaller than microbubbles obtained in a room air environment. These smaller microbubbles are more stable than microbubbles manufactured in a room air environment and result in improved delivery of the biologic.